This invention relates generally to devices for digitizing coordinates of a three-dimensional object, and more particularly to an apparatus for digitizing linear and planar structures exhibited in a core sample taken from the earth.
Apparatus for digitizing the coordinates of a two-dimensional figure with an electromagnetic coupling are known in the art. Such drawing and digitizing devices typically comprise a movable carriage or "mouse" which is free to move along a surface of a digitizing table. A cursor on the mouse may be placed at point on the figure to be digitized. Alternatively, the cursor may be used to trace a line on the figure for continuous digitizing. The mouse contains two electromagnetic coils which are used to produce signals indicative of the location of the mouse on the digitizing table. Such digitizing devices are only capable of determining the mouse location in two dimensions. Since the position of the cursor is restricted with respect to the digitizing table, such devices are incapable of digitizing the coordinates of a three-dimensional body.
Other devices are known for digitizing three-dimensional objects; however, these devices only employ optical couplings, acoustic couplings, manual measurements, or measurements using potentiometers and the like for determining the coordinates of the three-dimensional body.
The art of electromagnetically digitizing objects in three-dimensions has been developed by the McDonnell Douglas Corporation of St. Louis, Mo. and is disclosed in U.S. Pat. No. 4,613,866 issued Sept. 23, 1986. This device uses a hand held stylus for tracing and identifying points of interest on the surface of a stationary object. An electromagnetic source is provided immediately below a work surface upon which the object rests. A plurality of coils located within the source sequentially generate three-orthogonal electromagnetic fields, each of which are detected by similar coils located within a hand-held stylus which provides an output signal. This is output to an electronic analyzer which converts the components of the electromagnetic fields detected by the coils into a position and orientation of the stylus relative to a reference coordinate frame, thus, the coordinates of the object's surface are determined by the analyzer.
A disadvantage of this device is that the objects to be digitized must remain stationary within the electromagnetic field. Therefore, the operator must work around the object to digitize all surfaces. In the art of core analysis used in petroleum exploration, linear and planar structures of core sample have traditionally been measured manually. The information gathered from these studies were hand computed or entered into a computer for analysis. This is still very much the case today. No methods exist in core analysis for directly and quickly identifying and determining structures exhibited in core samples.